MDS PREP
What is the maximum allowable level of mercury in the blood?
1) 0.5 µg/L
2) 3 µg/L
3) 5 µg/L
4) 10 µg/L
The maximum allowable level of mercury in the blood is 3 µg/L according to the given text.
What is the typical composition of the mica crystals in a fluoromica glass ceramic like Dicor?
1) SiO2 · K2O · MgO · Al2O3 · ZrO2
2) Al2O3 · K2O · Na2O · MgO · ZrO2
3) SiO2 · CaO · Al2O3 · ZrO2
4) Al2O3 · Na2O · MgO · CaO
Fluoromica glass ceramics like Dicor have a composition based on mica crystals consisting of silica, potassium oxide (K2O), magnesium oxide (MgO), and aluminum oxide (Al2O3), with zirconium oxide (ZrO2) added for stability. Fluorides are included in the mixture to achieve fluorescence in the finished prosthesis. The material is castable and shares some similarities with traditional dental ceramics but with unique properties derived from its crystalline structure.
Which of the following is not a type of oil-based cement?
1) Zinc oxide-eugenol
2) Zinc phosphate
3) Nano-eugenol-zinc oxide
4) All of the above are oil-based cements
Zinc oxide-eugenol is the only oil-based cement mentioned in the text.
What is the typical concentration range of phosphoric acid used for enamel etching?
1) 10-20%
2) 20-30%
3) 30-40%
4) 35-50%
Phosphoric acid concentrations between 20% and 30% are commonly used for acid etching of enamel to create a roughened surface for mechanical bonding of restorative materials.
What is the main advantage of using Ormocers in dental restorations?
1) They have a high coefficient of thermal expansion.
2) They have excellent biocompatibility and resistance to masticatory loading.
3) They are easy to manipulate and require minimal finishing.
4) They can be used in high-stress bearing areas without reinforcement.
The main advantage of using Ormocers is their excellent biocompatibility and resistance to masticatory loading. They also have good esthetic properties, resembling those of natural teeth.
What are the three physical properties controlled by the ANSUADA Specification No. 1 (ISO 24234) for dental amalgam?
1) Creep, tensile strength, and thermal expansion.
2) Compressive strength, hardness, and density.
3) Creep, compressive strength, and dimensional change.
4) Tensile strength, modulus of elasticity, and corrosion resistance.
The specification controls the qualities of dental amalgam by listing requirements for creep, compressive strength, and dimensional change.
What are the main components of a typical dental composite resin?
1) Monomers, fillers, initiators, and accelerators.
2) Resins, fillers, catalysts, and diluents.
3) Polymers, pigments, and plasticizers.
4) Monomers, fillers, and cross-linking agents.
Dental composite resins typically consist of a resin matrix (monomers), filler particles (such as silica or glass), initiators (like camphorquinone), and accelerators (such as amines) to control the setting process.
Brinnel hardness number of a dental gold alloy is directly proportional to its:
1) Tensile strength
2) Elongation
3) Modulus of elasticity
4) Modulus of resiLience
Dental Materials Answer: 1
Brinnel and Rockwell tests are cLassified as macrohardness tests and they aie not suitable for brittle materials.
The Knoop and Vickers tests are classified as microhardness tests. Both of these tests employ toads less than 9.8N.
The Shore and the Barcot tests are used for measuring the hardness of rubbers and plastics.
The Bnnnel test is the one of oldest tests used for determining the hardness of materials and is directly related to proportional limit and the ultimate tensile strength of dental gold alloys.
The convenience of the Rockwell test, with direct reading of the depth of the indentation, has lead to its wide usage.
The Knoop hardness test is used to obtain the values for both exceedingly hard and soft materials. The hardness value is independent of the ductility of the material.
The Vickers test is employed for dental costing gold alloys. It is suitable for determining the hardness of brittle materials.